Reduced shear cellulose reactive sizing agent for wet end applications

ABSTRACT

The invention relates to a method for sizing a paper product that involves the steps of (a) providing a paper stock system; (b) forming, in the absence of high shearing forces, an aqueous sizing emulsion comprising an alkenylsuccinic anhydride component; (c) submitting the emulsion formed from step b to a post-dilution step in the presence of a cationic component under conditions, in the absence of high shearing forces, that produce a post-diluted emulsion having improved sizing efficacy; (d) adding the post-diluted emulsion to the paper stock; and (e) forming a paper web.

BACKGROUND

It is well known that the property of sizing, as applied to paper, refers to a fibrous substrate's ability to resist wetting or penetration of a liquid into a paper sheet. Aqueous dispersions of alkenylsuccinic anhydride cellulose-reactive sizing agent have been widely used in the paper and board making industry for many years, for sizing a wide variety of grades which include printing and writing grades and bleached and unbleached board grades. Cellulose-reactive alkenylsuccinic anhydride imparts hydrophobic properties to, the paper and board products.

Chemicals used to achieve sizing properties are known as either internal sizes or surface sizes. Internal sizes can be either rosin-based or synthetic sizes such as alkenylsuccinic anhydride, or other materials. Internal sizes are added to the paper pulp prior to sheet formation. Surface sizes are sizing agents that are added after the paper sheet has formed, most generally at the size press, although spraying applications may also be used.

Alkenylsuccinic anhydride sizing agent is ordinarily applied by dispersing it in a cationic or amphoteric hydrophilic substance such as a starch or a polymer. The starch or polymer-dispersed alkenylsuccinic anhydride sizing emulsion is added to the pulp slurry before the formation of a paper web. This type of addition of alkenylsuccinic anhydride sizing emulsions to the papermaking system is commonly called wet-end addition or internal addition of alkenylsuccinic anhydride.

Application of wet end applied cellulose reactive sizing agents such as alkenyl succinic anhydride using traditional emulsification methods has the following disadvantages: ASA emulsification in cationic starch needs a high starch/size ratio for emulsification. Also, in addition to the foregoing problem, the starch needs to be an high quality starch suitable for producing a stable, high quality ASA emulsion. ASA emulsification in cationic polymer or starch-grafted polymer also uses a lower polymer/size ratio than for starch, but a polymer that provides a stable, high quality ASA emulsion is needed for emulsification. Also the traditional emulsification of ASA in starch or polymer solution requires high shear conditions.

It would be desirable to develop an improved method of sizing paper at the wet end that will use a simpler and less expensive, low shear equipment for the ASA emulsification.

SUMMARY

The invention relates to method for sizing a paper product that involves the steps of: (a) providing a paper stock system; (b) forming, in the absence of high shearing forces, an aqueous sizing emulsion comprising an alkenyl succinic anhydride component; (c) submitting the emulsion formed from step b to a post-dilution step in the presence of a cationic component under conditions, in the absence of high shearing forces, that produce a post-diluted emulsion having improved sizing efficacy; (d) adding the post-diluted emulsion to the paper stock; and (e) forming a paper web.

In one embodiment, the invention relates to a paper made by the above-mentioned process.

In one embodiment, the invention relates to a method for sizing a paper product comprising:

-   -   (a) providing a paper stock system;     -   (b) forming, in the absence of high shearing forces, an aqueous         sizing emulsion comprising an alkenylsuccinic anhydride         component;

wherein the emulsion is made in the presence of a cationic component under conditions, in the absence of high shearing forces, that produce an emulsion having improved sizing efficacy;

-   -   (d) adding the emulsion to the paper stock; and     -   (e) forming a paper web.

These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims.

DESCRIPTION

Other than in operating examples or where otherwise indicated, all numbers or expressions referring to quantities of ingredients, reaction conditions, and the like, used in the specification and claims are to be understood as modified in all instances by the term “about.” Various numerical ranges are disclosed in this patent application. Because these ranges are continuous, they include every value between the minimum and maximum values. Unless expressly indicated otherwise, the various numerical ranges specified in this application are approximations.

The emulsion prepared prior to the post-dilution step includes an alkenylsuccinic anhydride-containing emulsion, which when subjected to a post-dilution step, improves sizing efficacy as compared to an emulsion that is not subjected to a post-dilution step. The emulsion, for instance, can include an alkenylsuccinic anhydride component containing alkenylsuccinic anhydride particles suspended in a starch component containing emulsifying starch selected from the group consisting of non-ionic starches, anionic starches, cationic starches and mixtures thereof. Starches that are used for the emulsification can be based on corn, potato, wheat, tapioca, or sorghum, and they could be modified through the use of enzymes, high temperature or chemical/thermal converting techniques.

Alternatively, the emulsion can include an alkenylsuccinic anhydride component containing alkenylsuccinic anhydride particles suspended in an aqueous polymer solution selected from the group of cationic polymers, nonionic polymers, anionic polymers, vinyl addition polymers, condensation polymers, and mixtures thereof. In one version of the invention, the invention includes an alkenylsuccinic anhydride component containing (i) alkenylsuccinic anhydride particles and (ii) surfactant component; suspended in water.

The emulsion of step (b) can be made by any suitable method. Generally, the emulsion is made with an emulsifying agent, e.g., a surfactant. Cationic polymer or cationic starch may be present, but they are not required. The weight ratio of the alkenylsuccinic anhydride to polymer or starch solids generally ranges from 1 to 0.02 to 1:1, or from 1 to 0.05 to 1 to 0.5, or from 1 to 0.1 to 1 to 0.2. In one embodiment, for instance, the emulsion in step (b) can be made by emulsifying an alkenylsuccinic anhydride component containing (i) alkenylsuccinic anhydride and (ii) a surfactant component, with water; and thereby forming an emulsion having an alkenylsuccinic anhydride component containing (i) alkenylsuccinic anhydride particles and (ii) a surfactant component; suspended in water. Alternatively, the emulsion in step (b) can be made by emulsifying an alkenylsuccinic anhydride component, optionally containing a surfactant, with an aqueous polymer solution, and thereby forming the emulsion. The sizing emulsion can be formed with a polyoxyalkylene alkyl ether or one surfactant selected from the group consisting of sulfosuccinates, alkyl and aryl amides and primary, secondary and tertiary amines and their corresponding quaternary salts, fatty acids, ethoxylated fatty acids, fatty alcohols, ethoxylated fatty alcohols, fatty esters, ethoxylated fatty esters, ethoxylated triglycerides, certain ethoxylated lanolin, sulfonated amines, sulfonated amides, ethoxylated polymers, propoxylated polymers, ethoxylated/propoxylated copolymers, polyethylene glycols, phosphate esters, phosphonated fatty acid ethoxylates, phosphonated fatty alcohol ethoxylates, alkyl sulfonates, aryl sulfonates, alkyl sulfates, aryl sulfates, and combinations thereof.

The polymer used to emulsify the alkenylsuccinic anhydride can be any polymer, which when used in accordance with the invention, can produce an emulsion in accordance with the invention. Examples of suitable polymers used in the emulsion of this sizing composition include polymeric stabilizers that include vinyl addition and condensation polymers having anionic, cationic, non-ionic and amphoteric charge characteristics with a charge substitution range varying from 0 to about 90%, and more preferably from 0 to about 10%. Further, the molecular weight of aforementioned synthetic polymeric stabilizer generally falls within the value ranging from about 10,000 to about 10 million daltons, or from about 100,000 to about two million or from about 200,00 to about 1 million daltons. All molecular weights mentioned herein are weight average.

Generally, suitable water-soluble polymers of this instant invention are cationic vinyl addition polymers, anionic vinyl addition polymers, neutral polymers, ampholytic polymers and condensation polymers.

Examples of suitable polymers include, water-soluble polymers having molecular weights ranging from 10,000 daltons to 3,000,000 daltons. The substantially water-soluble polymers to be used in this invention are comprised of but not limited to homopolymers and copolymers, and combinations thereof leading to terpolymers, and tetrapolymers comprised of the following monomers: acrylamide, diallyldimethylammonium chloride, dimethylaminoethylacrylate, dimethylaminoethylacrylate quaternaries, diethylaminoethyl acrylate, diethylaminoethylacrylate quaternaries, dimethylaminoethylmethacrylate, dimethylaminoethylmethacrylate quaternaries, dimethylaminoethylmethacrylate and its quaternaries, methacrylamidopropyltrimethyl ammonium chloride, acrylic acid. Suitable polymers also include polymers and copolymers of acrylamide that have been subjected to the “Mannich” reaction. Also, in one embodiment, the corresponding Mannich quaternaries are possible water-soluble polymers. Examples of other water-soluble polymers include copolymers comprised of substantially water-soluble and water dispersible styrene-alkylacrylates, styrene alkylacrylics, styrene maleic acid, styrene-maleic acid amide, styrene maleic acid esters, styrene maleic acid amide ester, and their corresponding salts. In another embodiment, suitable polymers include aqueous dispersions containing combinations of the reaction products of the above monomers, polyurethane dispersions with polyvinyl alcohol, poly vinylalcohol-vinylamine), their corresponding acetates or formamates or partially hydrolyzed polymers, or polyvinylamine.

Examples include copolymers of N,N-dialkylamino-alkyl(meth) acrylates and/or amides and/or alkyl(meth)acrylates, styrene, isobutylene, diisobutylene, vinyl acetate and/or acrylonitrile. Examples include condensation polymers of trimethylene diamine and 1,2-dichloroethane or 1,3 dichloropropane; adipic acid with diethylenetriamine, tetraethylenepentamine or similar polyalkylene; polyamides; subsequent reaction products with epichlorohydrin; dimethylamine-epichlorohydrin; ethylenediamine polyacrylamide. Examples include polyvinyl pyridine, poly-N-methylpyridinium chloride; poly-p-chlorostyrene quaternized with trialkylamine. Examples of such suitable polymers are described in U.S. Pat. Nos. 4,657,946, 4,784,727, 3,445,330, 6,346,554, incorporated herein by reference in their entirety.

Natural polymers, gums, and their extracts included in the embodiments of the invention may be taken from the following list: guar, acacia, agar, algin, carrageenan, cellulose and its derivatives, chitin, chitosan, damar, dextran, dextrin, ethylcellulose, gelatin, gellan, jalap, karaya, kelp, locust bean, methylcellulose, olibanum, pectin, rhamsan, sandarac, tragacanth, welan, and xanthan. This includes the salts and derivatives of the natural polymers. The polymers may be in their natural state or derivatized thereafter to form salts or other derivatives (e.g. hydroxyethylated). The products may be anionic, cationic, amphoteric, or neutral.

The emulsion may be made in the absence of high shearing forces (low shear conditions), e.g., those shearing conditions are created by a device selected from the group of centrifugal pumps, static in-line mixers, peristaltic pumps, and combinations thereof.

The alkenylsuccinic anhydride component generally includes alkenylsuccinic anhydride compounds composed of mono unsaturated hydrocarbon chains containing pendant succinic anhydride groups. The alkenylsuccinic anhydride compounds are generally liquid and may be derived from maleic anhydride and suitable olefins. The alkenylsuccinic anhydride compounds may be solid.

Generally speaking, the alkenylsuccinic anhydride compounds may be made by reacting an isomerized C₁₄-C₂₀ mono olefin, preferably an excess of an internal olefin, with maleic anhydride, at a temperature and for a time sufficient to form the alkenylsuccinic anhydride compound.

If the olefin to be employed in the preparation of the alkenylsuccinic anhydride compounds is not an internal olefin as is the case for example, with α-olefins, it may be preferable to first isomerize the olefins to provide internal olefins. The olefins that may be used in the preparation of the alkenylsuccinic anhydride compounds may be linear or branched. Preferably, the olefins may contain at least about 14 carbon atoms. Typical structures of alkenylsuccinic anhydride compounds are disclosed, for example, in U.S. Pat. No. 4,040,900, incorporated herein by reference in its entirety. Alkenylsuccinic anhydride compounds and methods for their preparation are described, for example, in C. E. Farley and R. B. Wasser, “The Sizing of Paper, Second Edition,” edited by W. F. Reynolds, TAPPI Press, 1989, pages 51-62, the disclosures of which are hereby incorporated herein by reference in its entirety.

The alkenylsuccinic anhydride component may contain some hydrolyzed alkenylsuccinic anhydride. The amount of hydrolyzed alkenylsuccinic anhydride may range from about 1 to about 30 wt. %, based on the total weight of the alkenylsuccinic anhydride component.

The alkenylsuccinic anhydride component can include:

a. from 80 to 97 parts of substituted cyclic dicarboxylic acid anhydride corresponding to the formula

wherein R represents a dimethylene or trimethylene radical and wherein R′ is a hydrophobic group containing more than 5 carbon atoms which may be selected from the class consisting of alkyl, alkenyl, aralkyl, or aralkenyl groups;

wherein R_(x) is an alkyl radical containing at least 5 carbon atoms and R_(y) is an alkyl radical containing at least 5 carbon atoms, and R_(x) and R_(y) are interchangeable;

wherein R_(x) is an alkyl radical containing at least 5 carbon atoms and R_(y) is an alkyl radical containing at least 5 carbon atoms and R_(x) and R_(y) are interchangeable; and

b. from 3 to 20 parts of a polyoxyalkylene alkyl or polyoxyalkylene alkyl-aryl ether or the corresponding mono- or diester selected from the group consisting of:

wherein x and n are integers in the range of 8 to 20; R is an aryl radical; m is an integer in the range of 5 to 20; and i is 0, 1, or 2.

The alkenylsuccinic anhydride component is generally present in the emulsion in an amount that is at least about 0.01 wt. %, or from about 0.1 to about 20 wt. %, or from about 0.3 wt. % to about 15 wt. %, based on the total weight of the emulsion. The emulsion generally contains alkenylsuccinic anhydride particles ranging from 0.5 microns to less than 3 microns.

When a surfactant is used to make the emulsion, the surfactant component includes surfactants, which when used to make an emulsion in accordance with the invention, produces an emulsion that minimizes coalescing and imparts useful sizing properties to a fibrous substrate after the emulsion contacts the fibrous substrate. The surfactant component functions as an emulsifying agent when the emulsion is made. The surfactant component facilitates the emulsification of the alkenylsuccinic anhydride with the water component when the emulsion is made. Generally, the surfactants are anionic or nonionic or can be cationic and can have a wide range of HLB values.

Examples of suitable surfactants include but are not limited to alkyl and aryl primary, secondary and tertiary amines and their corresponding quaternary salts, sulfosuccinates, fatty acids, ethoxylated fatty acids, fatty alcohols, ethoxylated fatty alcohols, fatty esters, ethoxylated fatty esters, ethoxylated triglycerides, sulfonated amides, sulfonated amines, ethoxylated polymers, propoxylated polymers or ethoxylated/propoxylated copolymers, polyethylene glycols, phosphate esters, phosphonated fatty acid ethoxylates, phosphonated fatty alcohol ethoxylates, and alkyl and aryl sulfonates and sulfates. Examples of preferred suitable surfactants include but are not limited to amides; ethoxylated polymers, propoxylated polymers or ethoxylated/propoxylated copolymers; fatty alcohols, ethoxylated fatty alcohols, fatty esters, carboxylated alcohol or alkylphenol ethoxylates; carboxylic acids; fatty acids; diphenyl sulfonate derivatives; ethoxylated alcohols; ethoxylated fatty alcohols; ethoxylated alkylphenols; ethoxylated amines; ethoxylated amides; ethoxylated aryl phenols; ethoxylated fatty acids; ethoxylated triglycerides; ethoxylated fatty esters; ethoxylated glycol esters; polyethylene glycols; fatty acid esters; glycerol esters; glycol esters; certain lanolin-based derivatives; monoglycerides, diglycerides and derivatives; olefin sulfonates; phosphate esters; phosphorus organic derivatives; phosphonated fatty acid ethoxylates, phosphonated fatty alcohol ethoxylates; polyethylene glycols; polymeric polysaccharides; propoxylated and ethoxylated fatty acids; alkyl and aryl sulfates and sulfonates; ethoxylated alkylphenols; sulfosuccinamates; sulfosuccinates.

In one embodiment, the surfactant component includes an amine selected from the group consisting of trialkyl amine of the formula (I):

dimethyl sulfate quaternary salt of trialkyl amine of the formula (I), benzyl chloride quaternary salt of trialkyl amine of the formula (I), and diethyl sulfate quaternary salt of trialkyl amine of the formula (I), in which R₁ is methyl or ethyl, R₂ is methyl or ethyl, and R₃ is alkyl having 14 to 24 carbon atoms. In another embodiment, the surfactant excludes this amine.

The surfactant levels can range from about 0.1 weight % up to about 20 weight % based on the alkenylsuccinic anhydride component.

It has been discovered that the following examples do not provide suitable results (produce paper products with useless sizing properties) under certain conditions: sorbitan monolaurate (Arlacel 20), ethoxylated sorbitan trioleate (Tween 85), propoxylated lanolin (Solulan PB-5), ethoxylated lanolin (Laneto 100), sorbitan trioleate (Span 85), isostearic alkanolamide (Monamid 150-IS), hydroxylated milk glycerides (Cremophor HMG), bis(tridecyl) ester of sodium sulfosuccinic acid (AEROSOL® TR-70).

The post-dilution step generally involves mixing the emulsion with a cationic component at autogenous conditions. The cationic component can be selected from the group consisting of cationic starches, cationic polymers, cationic starch-grafted polymers, and mixtures thereof. Also, the cationic component can be selected from the group consisting of cationic vinyl addition polymers, cationic condensation polymers, and combinations thereof. Starches that are used for the post-dilutation step can be based on corn, potato, wheat, tapioca, or sorghum, and they could be modified through the use of enzymes, high temperature or chemical/thermal converting techniques. The starches that are used for the post-dilution have to be cationic.

The ratio of the cationic component solids to the alkenylsuccinic anhydride in the post-dilution step should range from 0.1:1 to 4:1, but in some cases could be as high as 50:1. This ratio will depend on the requirements for a specific paper production application.

The temperature at which the process of the invention can be carried out is generally less than 50° C. The pH at which the process of the invention is practiced varies, depending on the application. The pH, for instance, can range from 4 to 8 or from 6 to 8. The post-dilution step is generally carried out under low shear conditions e.g., those shearing conditions are created by a device such as selected from the group of centrifugal pumps static in-line mixers, peristatic pumps, magnetic stirring bar in a beaker, overhead stirrer, and combinations thereof. Although the post dilution step is typically carried out, in one embodiment, if alkenyl succinic anhydride is emulsified in a cationic component than the post-dilution with a second cationic component is optional.

The duration of the mixing in step(c) generally occurs less than one minute. For instance, the mixing in step(c) can occur from 1 to 20 seconds.

The stability of the post-diluted composition varies. For instance, the stability of the post-diluted composition can be stable from 1 to 6 hours.

The method of the invention provides valuable advantages. For instance, the paper sized in accordance with the invention generally exhibits a sizing efficiency that is more than 20% higher, as compared to paper made with a composition that is not subjected to a post-dilution step. The paper that can be sized with the method of the invention can be selected from the group consisting of paperboard papers, fine papers, newsprint papers, and combinations thereof.

As such, the invention can also be directed to the papers treated with Applicants' invention.

The invention is further described in the following illustrative examples in which all parts and percentages are by weight unless otherwise indicated.

EXAMPLES Handsheets Studies Examples 1-12

Evaluation of a low shear alkenylsuccinic anhydride (ASA) performance was done by preparation of ASA emulsions with water, polymers or starch, characterization of the emulsion particle size distribution, addition of these emulsions to the paper furnish, forming paper handsheets and measuring the sizing of paper handsheets. The performance of the low shear emulsion was compared to a conventional, high shear ASA emulsion.

Emulsification of Low Shear ASA in Water Using a Centrifugal Pump—Method 1

Alkenylsuccinic anhydride (ASA) containing 5% Brij® 98 surfactant was emulsified in water with a single impeller, open-feed, 1-horsepower centrifugal pump at a speed of 1700 rpm. The low shear centrifugal pump was connected to a tap water supply and the pump was operated using the pressure from the tap water supply. No pH or temperature adjustment was made to the tap water prior to emulsification. ASA was supplied to the centrifugal pump from a calibration column via a gear pump. ASA entered the water inlet just before the centrifugal pump. The water flow rate was approximately 1 L/min and ASA flow rate was approximately 240 mL/min. The centrifugal pump was a single-pass emulsification process with no recirculation. The resulting ASA emulsion contained 19 weight percent ASA.

Emulsification of Low Shear ASA in Polymer or Starch Solution Using a Centrifugal Pump—Method 2

The emulsification of ASA containing 5% Brij 98 surfactant in polymer or starch solution was done as the emulsification in water, except that polymer or starch were added to a water line using a variable speed gear pump, and it was mixed using an in-line static mixer before it was combined with ASA flow. The centrifugal pump was run at a speed between 1700 and 3600 rpm. The concentration of ASA in the emulsion varied from about 3 to about 10 wt %, depending on particular study. The total flow rate of water, ASA and polymer or starch was about 1 L/min.

Emulsification of ASA with High Shear

A high shear ASA, BAYSIZE® I 18 size (LANXESS Corporation) emulsion were prepared with a polymer or starch solution using a household blender on high speed for 90-180 sec. See details in examples.

Emulsion Particle Size Analysis

A commercially available, light scattering, particle analyzer, Horiba LA-300 was used to determine the particle size of the emulsions. Results are reported as the median particle size in microns.

Handsheet Preparation Process Used in Examples 1-10

Handsheets were prepared using a furnish of a 50/50 mixture of bleached hardwood and softwood kraft pulp refined to a Canadian Standard Freeness (CSF) of 500 mL to which 10% by weight of precipitated calcium carbonate was added, and pH was adjusted to 7.8.

Deionized water was used for furnish preparation and additional 80 ppm of sodium sulfate and 50 ppm of calcium chloride were added.

While mixing, a batch of pulp at 0.71% solids containing 17 g of cellulose fibers and calcium carbonate was treated with an ASA emulsion that was diluted to 0.25 wt. % with tap water. Alum was also added to the batch and applied at a dose of 5 lb per ton of dry fiber. Alum was applied 30 sec prior to ASA emulsion addition. After a 60-sec contact time, 1 lb per ton on dry fiber of an anionic retention aid was added, and mixing continued for 15 sec.

Three 5.0 g sheets of paper were formed using a standard (8″×8″) Nobel & Woods handsheet mold, to target a basis weight of 121 g/m². Each sheet was pressed between felts in the nip of a pneumatic roll press at about 15 psig and dried on a rotary dryer at 240° F.

Paper Sizing Evaluation Procedures

A 2-min Cobb test or Ink Penetration Holdout test was used to evaluate the sizing paper.

2-Min Cobb Test

The sizing of handsheets was tested using a 2-min Cobb test. The test was performed according to TAPPI Test Method T441 om-90. A 100-cm² ring was utilized in this test.

Ink Penetration Holdout

Ink Penetration Holdout was measured using a method similar to that described in TAPPI Method T 530 pm-89 except that an instrument was used as described in U.S. Pat. No. 5,483,078. The test measures the time (in seconds) for the reflectance of the paper on the side opposite that contacting the ink to decreases to 80% of the initial value. The ink consists of 1.25% Naphthol Green B dye buffered to pH 7. The test values were normalized for basis weight of the paper assuming that the values vary as the cube of the basis weight. Results were expressed in units of seconds.

Example 1

ASA containing 5 wt % of Brij 98 surfactant was emulsified in an aqueous solution of the high molecular weight cationic acrylamide polymer, BAYSIZE® E LS polymer (LANXESS Corporation) at a sizing agent to polymer solids ratio of 1/0.1.

The emulsification was done according to Method 2, using a centrifugal pump at a speed of 3000 rpm. During the emulsification process, the ASA flow was 53 mL/min, the 10.8% (w/w) polymer solution flow was 47 mL/min, and water flow was 1030 mL/min. The sizing agent concentration in the emulsion was 4.88% (w/w). The emulsion particle size was 1.18 microns. The handsheets were prepared with this emulsion and the sizing of these handsheets was measured using a 2-min Cobb test.

Example 2 (Comparative)

BAYSIZE I 18 size (LANXESS Corporation) was emulsified in the aqueous solution of the high molecular weight cationic acrylamide polymer BAYSIZE E LS polymer (LANXESS Corporation) at a sizing agent to polymer solids ratio of 1/0.1. During the emulsification process, 20.2 g of BAYSIZE I 18 size (LANXESS Corporation) was added to 100 g of 2.02 (w/w) polymer solution and mixed in a household blender on high speed for 3 min. The emulsion particle size was 0.72 microns. The handsheets were prepared with this emulsion and the sizing of these handsheets was measured using a 2-min Cobb test.

TABLE 1 Performance of Sizing Agents Emulsified with a High Molecular Weight Cationic Polymer. 2-min Cobb Sizing (g/m²) 4.25 lb/t of 4.25 lb/t of 5.25 lb/t of 6.25 lb/t of sizing agent; Example sizing agent sizing agent sizing agent 5 lb/t of alum Example 1 54.5 35 30.5 26.5 Example 2 38.0 28.5 30.0 25.5 (compara- tive)

The emulsion of a low shear ASA (Example 1) provided worse paper sizing than the high shear ASA emulsion (Example 2) at a low sizing agent dose, but as the dose was increased or as 5 lb/t of alum was applied, the sizing performance of both sizing agents was equivalent.

Example 3

ASA containing 5% (w/w) of Brij 98 surfactant was emulsified in the aqueous solution of the low molecular weight cationic acrylamide polymer BAYSIZE® E HE polymer (LANXESS Corporation) at a sizing agent to polymer solids ratio of 1/0.15.

The emulsification was done according to Method 2, using a centrifugal pump at a speed of 1700 rpm. During the emulsification process, the ASA flow was 50 mL/min, the 26-wt. % polymer solution flow was 26 mL/min, and water flow was 1909 mL/min. The sizing agent concentration in the emulsion was 4.8 wt. %. The emulsion particle size was 2.3 microns. The handsheets were prepared with this emulsion, and the sizing of these handsheets was measured using a 2-min Cobb test.

Example 4 (Comparative)

BAYSIZE I 18 size (LANXESS Corporation) was emulsified in the aqueous solution of the low molecular weight cationic acrylamide polymer BAYSIZE E HE polymer (LANXESS Corporation) at a sizing agent to polymer solids ratio of 1/0.15. During the emulsification process, 20.2 g of BAYSIZE I 18 size (LANXESS Corporation) was added to 101 g of 3% (w/w) polymer solution and mixed in a household blender on high speed for 3 min. The emulsion particle size was 1.1 microns. The handsheets were prepared with this emulsion, and the sizing of these handsheets was measured using a 2-min Cobb test.

TABLE 2 Performance of Sizing Agents Emulsified with a Low Molecular Weight Cationic Polymer. 2-min Cobb Sizing (g/m²) 4.5 lb/t of 4.5 lb/t of 5.5 lb/t of 6.5 lb/t of sizing agent, Example sizing agent sizing agent sizing agent 5 lb/t of alum Example 3 104.5 73.0 28.0 25.5 Example 4 66 36.5 29.5 26.5 (compara- tive)

The sizing performance of the low shear ASA emulsified with the low molecular weight cationic polymer (Example 3) matched the performance of the high shear ASA emulsified with the same low molecular cationic polymer (Example 4) when a higher dose of sizing agent was used. The sizing performance was also matched when a lower dose of sizing agent was used in conjunction with alum.

Example 5

ASA containing 5% (w/w) of Brij 98 surfactant was emulsified in a solution of Hi-Cat CWS pregelatinized starch (Roquette) at a sizing agent to starch solids ratio of 1/1. The emulsification was done according to Method 2, using a centrifugal pump at a speed of 2400 rpm. During the emulsification process, the ASA flow was 44.5 mL/min, the 4.19% (w/w) starch solution flow was 955.5 mL/min, and there was no water flow. The sizing agent concentration in the emulsion was 4.21% (w/w). The emulsion particle size was 3.6 microns. The handsheets were prepared with this emulsion, and the sizing of these handsheets was measured using a 2-min Cobb test.

Example 6

ASA containing 5% (w/w) of Brij 98 surfactant was emulsified in tap water.

The emulsification was done according to Method 1, using a centrifugal pump at a speed of 1700 rpm. During the emulsification process, the ASA flow was 44.5 mL/min, the water flow was 955.5 mL/min. The sizing agent concentration in the emulsion was 4.2% (w/w). The emulsion particle size was 1.5 microns. The emulsion was post-diluted with the 4.19% (w/w) solution of Hi-Cat CWS pregelatinized starch (Roquette). The sizing agent to starch solids ratio in the post-diluted emulsion was 1/1. The handsheets were prepared with this emulsion, and the sizing of these handsheets was measured using a 2-min Cobb test.

Example 7 (Comparative)

BAYSIZE I 18 size (LANXESS Corporation) was emulsified in an aqueous solution of Hi-Cat CWS pregelatinized starch (Roquette) at a sizing agent to starch solids ratio of 1/1.

During the emulsification process, 8.08 g of BAYSIZE I 18 size (LANXESS Corporation) was added to 191.92 g of the 4.19% (w/w) starch solution and mixed in a household blender on high speed for 90 seconds. The emulsion particle size was 0.62 microns.

The handsheets were prepared with this emulsion, and the sizing of these handsheets was measured using a 2-min Cobb test.

TABLE 3 Performance of Sizing Agents Emulsified in Starch or Post-diluted with Starch. 2-min Cobb Sizing (g/m²) 4.25 lb/t of 5.25 lb/t of 6.25 lb/t of Example sizing agent sizing agent sizing agent Example 5 44.0 26.5 27.0 Example 6 137.5 72.5 33.5 Example 7 34.0 27.0 25.5 (comparative)

The low shear ASA emulsified in a cationic starch solution (Example 5) provided similar performance to the high shear ASA emulsified in the same starch solution (Example 7). Worse performance was achieved when the low shear ASA was emulsified in water and post-diluted with starch solution to provide the sizing agent to starch solids ratio of 1/1.

Example 8

The amount of 6.0 g of ASA containing 5 wt % of Brij 98 surfactant was emulsified with 114 g of 0.53% (w/w) aqueous solution BAYSIZE® E HE polymer (LANXESS Corporation), using a household blender on low speed for 30 second. The emulsion particle size was 1.3 microns. The handsheets were prepared with this emulsion. During the handsheets making process, each set was treated with 5 lb/t of alum. The sizing of these handsheets was measured using a 2-min Cobb test.

Example 9

ASA, 6.0 g, containing 5% (w/w) of Brij 98 surfactant was emulsified in 114.0 g of tap water, using a household blender on low speed for 30 second. The emulsion particle size was 0.95 microns. Ten grams of the emulsion was post-diluted with 190 g of 0.026-wt. % aqueous solution of the low molecular weight cationic acrylamide polymer BAYSIZE E HE polymer (LANXESS Corporation). The handsheets were prepared with this emulsion. During the handsheets making process, each set was treated with 5 lb/t of alum. The sizing of these handsheets was measured using a 2-min Cobb test.

Example 10 (Comparative)

BAYSIZE I 18 size (LANXESS Corporation) was emulsified in the aqueous solution of the low molecular weight cationic acrylamide polymer BAYSIZE E HE polymer (LANXESS Corporation) at a sizing agent to polymer solids ratio of 1/0.1. During the emulsification process, 20 g of BAYSIZE I 18 size (LANXESS Corporation) was added to 100 g of 2% (w/w) polymer solution and mixed in a household blender on high speed for 3 min. The emulsion particle size was 1.0 micron. The handsheets were prepared with this emulsion. During the handsheets making process, each set was treated with 5 lb/t of alum. The sizing of these handsheets was measured using a 2-min Cobb test.

TABLE 4 Performance of Sizing Agents Emulsified or Post-diluted with a Low Molecular Weight Cationic Polymer. 2-min Cobb Sizing (g/m²) 4.0 lb/t of 5.0 lb/t of 6.0 lb/t of sizing agent; sizing agent; sizing agent; Example 5 lb/t of alum 5 lb/t of alum 5 lb/t of alum Example 8 24.6 18.8 26.9 Example 9 35.0 27.4 15.3 Example 10 25.7 24.4 24.1 (comparative)

As this is shown in Table 4, the application of alum in the handsheets making process improved the performance of a low shear ASA. The performance of the low shear ASA emulsified in the low molecular weight cationic polymer (Example 8) provided comparable performance to the high shear ASA (Example 10) over the broad dose range. The low shear ASA that was emulsified in water and post-diluted with the polymer solution (Example 9) provided worse sizing than ASA emulsified with the polymer, but the difference in the performance was rather small.

Example 11

ASA, 6.0 g, containing 5% (w/w) of Brij 98 surfactant was emulsified in 114.0 g of tap water, using a household blender on low speed for 30 second. The emulsion particle size was 1.03 microns. The emulsion was post-diluted to 0.25% (w/w) with tap water, and than mixed with a 1% (w/w) cationic starch solution. The 82 g/m² basis weight handsheets were prepared with this emulsion. Handsheets were made with the recycled furnish obtained from a board mill. During the handsheet-making process, each set was first treated with polyaluminum chloride at a dose of 12 lb/t of dry fiber. After 30 sec, the mixture of ASA emulsion and starch was added to the furnish. The mixture of ASA emulsion provided 20 lb of dry starch per ton of dry fiber. After a 60-sec contact time, an anionic retention aid was added at a dose of 1 lb/t of dry fiber, and mixing continued for 15 sec. Ink Penetration Holdout was used to evaluate the paper sizing.

Example 12 (Comparative)

This example was like Example 11, except that the ASA emulsion and the starch solution was added separately to the furnish. ASA, 6.0 g, containing 5% (w/w) of Brij 98 surfactant was emulsified in 114.0 g of tap water, using a household blender on low speed for 30 sec. The emulsion particle size was 1.03 microns. The handsheets were prepared with this emulsion. Handsheets were made with recycled furnish. During the handsheet-making process, each set was first treated with polyaluminium chloride at a dose of 12 lb per ton of dry fiber. After 30 sec, the ASA emulsion was added and mixed with furnish for 5 sec before 20 lb of cationic starch per ton of dry fiber was added. After 55 sec, 1 lb of an anionic retention aid per ton of dry fiber was added, and mixing continued for 15 sec. Ink Penetration Holdout was used to evaluate paper sizing.

TABLE 5 Post-dilution of Low Shear ASA Emulsion with Starch vs. Separate Addition of ASA Emulsion and Starch to the Furnish. Neutral Ink Holdout (sec) 0.12 lb/t of 0.25 lb/t of 0.5 lb/t of Example sizing agent sizing agent sizing agent Example 11 308 740 2197 Example 12 240 259 354 (comparative)

The post-dilution of the low shear ASA emulsion with cationic starch solution prior to the addition of ASA emulsion to the furnish (Example 11) provided significantly higher paper sizing than the separate addition of ASA emulsion and starch to the furnish (Example 12).

Example 13-17

Evaluation of low shear alkenylsuccinic anhydride (ASA) performance was done by preparation of ASA emulsions in water or in a polymer solution, or post-dilution of ASA emulsified in water with starch or polymer solution, and addition of these emulsions to the paper furnish during a pilot machine paper making process. The sizing performance of the low shear emulsion was compared to a conventional, high shear ASA emulsion, using a 2-min Cobb test.

Paper Furnish

A 30/70 blend of bleached northern softwood Kraft refined to 420 mL CSF and bleached northern hardwood Kraft refined to 350 mL CSF was applied in the pilot machine papermaking process. Precipitated calcium carbonate was added to the machine chest in the amount of 10 wt. % on dry fiber. The basis weight of the paper produced on the pilot machine was 120 gm².

Pilot Paper Machine Operating Conditions

The pilot machine speed is 85 feet per minute, giving a production rate of about 1.16 lb/min. The pH of the paper furnish was maintained between 7.9 and 8.4. The ASA emulsions were diluted with tap water to 0.5% (w/w) concentration before the addition to the paper furnish. An anionic retention aid in the amount of 0.5 lb per ton of dry paper was applied. The paper moisture content was 4% (w/w) at the reel.

Example 13

ASA containing 5% (w/w) of Brij 98 surfactant was emulsified in an aqueous solution of the low molecular weight cationic acrylamide polymer BAYSIZE E HE polymer (LANXESS Corporation) at a sizing agent to polymer solids ratio of 1/0.12.

The emulsification was done according to Method 2, using a centrifugal pump at a speed of 3300 rpm. During the emulsification process, the ASA flow was 50 mL/min, the 13.27% (w/w) polymer solution flow was 40 mL/min, and water flow was 810 mL/min. The sizing agent concentration in the emulsion was 5.26% (w/w). The emulsion particle size was 1.17 microns. This emulsion was applied as an internal sizing agent to produce paper on the pilot paper machine. The sizing of the felt and wire side of this paper was measured using a 2-min Cobb test.

Example 14

ASA containing 5% (w/w) of Brij 98 surfactant was emulsified in tap water.

The emulsification was done according to Method 1, using a centrifugal pump at a speed of 1700 rpm. During the emulsification process, the ASA flow was 50.0 mL/min, the water flow was 850 mL/min. The sizing agent concentration in the emulsion was 5.26% (w/w). The emulsion particle size was 1.44 microns. The emulsion was post-diluted with the 0.05% (w/w) of BAYSIZE E HE polymer (LANXESS Corporation). The sizing agent to polymer solids ratio in the post-diluted emulsion was 1/0.1, and the ASA concentration was 0.5 wt. %. This emulsion was applied as an internal sizing agent to produce paper on the pilot paper machine. The sizing of the felt and wire side of this paper was measured using a 2-min Cobb test.

Example 15 (Comparative)

BAYSIZE I 18 size (LANXESS Corporation) was emulsified in the aqueous solution of the low molecular weight cationic acrylamide polymer BAYSIZE E HE polymer (LANXESS Corporation) at a sizing agent to polymer solids ratio of 1/0.1. During the emulsification process, 240 g of BAYSIZE I 18 size (LANXESS Corporation) was added to 180.86 g of a 13.25% (w/w) polymer solution and 1019.71 g of tap water, and the mixture stirred in an industrial blender on low speed for 1.5 min. The emulsion particle size was 1.15 microns. Handsheets were prepared with this emulsion. This emulsion was applied as an internal sizing agent to produce paper on the pilot paper machine. The sizing of the felt and wire side of this paper was measured using a 2-min Cobb test.

TABLE 5 Performance of Sizing Agents Emulsified with a Low Molecular Weight Cationic Polymer. Data from the Pilot Machine Trial. 2-min Cobb Sizing (g/m²) 4.0 lb/t of 5.0 lb/t of 4.0 lb/t of 5.0 lb/t of 6.0 lb/t of sizing agent; sizing agent, Example sizing agent sizing agent sizing agent 5 lb/t of alum 5 lb/t of alum Example 13 119.8 77.5 39.6 31.5 32 Example 14 49.5 Example 15 124.8 87.5 43.8 39.5 34.5 (comparative)

The low shear ASA (Example 13) provided slightly better sizing than the high shear ASA (Example 15) over a broad dose range when both sizing agents were applied at the wet-end of paper making process on the pilot machine. The low shear ASA emulsified in water and post-diluted with a cationic polymer solution (Example 14) provided a good sizing response, however the sizing was lower than the sizing obtained with the low shear ASA emulsified in the polymer solution (Example 13).

Example 16

ASA containing 5% (w/w) of Brij 98 surfactant was emulsified in tap water, as it was described in Example 14. The emulsion was post-diluted with a 2.2. % (w/w) solution of the Hi-Cat CWS pregelatinized starch (Roquette). The sizing agent to starch solids ratio in the post-diluted emulsion was 1/4, and the ASA concentration was 0.5% (w/w). This emulsion was applied as an internal sizing agent to produce paper on the pilot paper machine. The sizing of the felt and wire side of this paper was measured using a 2-min Cobb test.

Example 17 (Comparative)

BAYSIZE I 18 size (LANXESS Corporation) was emulsified in an aqueous solution of the Hi-Cat CWS pregelatinized starch (Roquette) at a sizing agent to starch solids ratio of 1/1. During the emulsification process, 80 g of BAYSIZE I 18 size (LANXESS Corporation) was added to 1920 g of 4.17% (w/w) starch solution and mixed in an industrial blender on low speed for 30 sec. The emulsion particle size was 1.37 microns. The emulsion was post-diluted with a 1.7% (w/w) solution of the Hi-Cat CWS pregelatinized starch (Roquette). The sizing agent to starch solids ratio in the post-diluted emulsion was 1/4, and the ASA concentration was 0.5% (w/w). The handsheets were prepared with this emulsion. This emulsion was applied as an internal sizing agent to produce paper on the pilot paper machine. The sizing of the felt and wire side of this paper was measured using a 2-min Cobb test.

TABLE 6 Performance of Sizing Agents Emulsified in Starch or Post-diluted with Starch. 2-min Cobb Sizing (g/m²) 4.0 lb/t of 7.0 lb/t of 8.0 lb/t of Example sizing agent sizing agent sizing agent Example 16 41.3 36.5 32.3 Example 17 29.8 (comparative)

The results in Table 6 indicate that the low shear ASA post-diluted with the cationic starch is less effective in terms paper sizing as the high shear ASA emulsified in the cationic starch. However, the simplicity of the emulsification process of the low shear ASA and acceptable sizing response gives the paper maker operational and cost benefits in using this system.

Although the present invention has been described in detail with reference to certain preferred versions thereof, other variations are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the versions contained therein. 

1. A method for sizing a paper product comprising: (a) providing a paper stock system; (b) forming, in the absence of high shearing forces, an aqueous sizing emulsion comprising an alkenylsuccinic anhydride component; (c) submitting the emulsion formed from step b to a post-dilution step in the presence of a cationic component under conditions, in the absence of high shearing forces, that produce a post-diluted emulsion having improved sizing efficacy; (d) adding the post-diluted emulsion to the paper stock; and (e) forming a paper web.
 2. The method of claim 1, wherein the emulsion in step (b) further comprises a surfactant component.
 3. The method of claim 1, wherein the emulsion in step (b) comprises an alkenylsuccinic anhydride component comprising alkenylsuccinic anhydride particles suspended in a starch component, wherein the starch component comprises an containing emulsifying starch selected from the group consisting of non-ionic starches, anionic starches, cationic starches, and mixtures thereof.
 4. The method of claim 3, wherein the emulsion in step (b) further comprises a surfactant component.
 5. The method of claim 1, wherein the emulsion in step (b) comprises an emulsion comprising alkenylsuccinic anhydride component comprising alkenylsuccinic anhydride particles suspended in an aqueous polymer solution, wherein the aqueous polymer solution is selected from the group consisting of cationic polymers, nonionic polymers, anionic polymers, vinyl addition polymers, condensation polymers, and mixtures thereof.
 6. The method of claim 5, wherein the emulsion in step (b) further comprises a surfactant component.
 7. The method of claim 1, wherein the emulsion in step (b) comprises an alkenylsuccinic anhydride component comprising (i) alkenylsuccinic anhydride particles and (ii) a surfactant component suspended in water.
 8. The method of claim 1, wherein the alkenyl succinic anhydride component in step (b) comprises: a. from 80 to 97 parts of substituted cyclic dicarboxylic acid anhydride corresponding to the formula

wherein R represents a dimethylene or trimethylene radical and wherein R′ is a hydrophobic group containing more than 5 carbon atoms;

wherein R_(x) is an alkyl radical containing at least 5 carbon atoms and R_(y) is an alkyl radical containing at least 5 carbon atoms, and R_(x) and R_(y) are interchangeable;

wherein R_(x) is an alkyl radical containing at least 5 carbon atoms and R_(y) is an alkyl radical containing at least 5 carbon atoms and R_(x) and R_(y) are interchangeable; and b. from 3 to 20 parts of a polyoxyalkylene alkyl or polyoxyalkylene alkyl-aryl ether or the corresponding mono- or diester selected from the group consisting of:

wherein x and n are integers in the range of 8 to 20; R is an aryl radical; m is an integer in the range of 5 to 20; and i is 0, 1, or
 2. 9. The method of claim 1, wherein the cationic component in step (c) is selected from the group consisting of cationic starches, cationic polymers, cationic starch-grafted polymers, and mixtures thereof.
 10. The method of claim 1, wherein the cationic component in step (c) is selected from the group consisting of cationic vinyl addition polymers, cationic condensation polymers, and combinations thereof.
 11. The method of claim 1, wherein the emulsion contains alkenylsuccinic anhydride particles ranging from 0.5 microns to less than 3 microns.
 12. The method of claim 1, wherein the sizing emulsion is formed with a surfactant component selected from the group consisting of sulfosuccinates, alkyl and aryl amides and primary, secondary and tertiary amines and their corresponding quaternary salts, fatty acids, ethoxylated fatty acids, fatty alcohols, ethoxylated fatty alcohols, fatty esters, ethoxylated fatty esters, ethoxylated triglycerides, ethoxylated lanolins, sulfonated amines, sulfonated amides, ethoxylated polymers, propoxylated polymers, ethoxylated/propoxylated copolymers, polyethylene glycols, phosphate esters, phosphonated fatty acid ethoxylates, phosphonated fatty alcohol ethoxylates, alkyl sulfonates, aryl sulfonates, alkyl sulfates, aryl sulfates, and combinations thereof
 13. The method of claim 1, wherein the post-dilution step comprises mixing the emulsion with an additive selected from the group consisting of cationic starches, cationic polymers, cationic starch-grafted polymers, and mixtures thereof at autogenous conditions.
 14. The method of claim 1, wherein the temperature is less than 50° C.
 15. The method of claim 1, wherein the mixing in step (c) occurs less than one minute.
 16. The method of claim 1, wherein the mixing in step (c) occurs from 1 to 20 seconds.
 17. The method of claim 1, wherein the paper exhibits a sizing efficiency that is more than 20% higher, as compared to paper made with a composition that is not subjected to a post-dilution step.
 18. The method of claim 17, wherein the paper is selected from the group consisting of paperboard papers, fine papers, newsprint papers, and combinations thereof.
 19. The method of claim 1, wherein the post-diluted composition is stable from 1 to 6 hours.
 20. The method of claim 1, wherein the emulsion in step (b) is made by emulsifying alkenylsuccinic anhydride with a first starch component comprising a starch selected from the group consisting of non-ionic starches, ionic starches, and mixtures thereof and thereby forming an emulsion.
 21. The method of claim 20, wherein the emulsion contains a surfactant component.
 22. The method of claim 1, wherein the emulsion in step (b) is made by emulsifying an alkenylsuccinic anhydride component containing (i) alkenylsuccinic anhydride and (ii) a surfactant component, with water; and thereby fowling an emulsion having an alkenylsuccinic anhydride component containing (i) alkenylsuccinic anhydride particles and (ii) a surfactant component suspended in water.
 23. The method of claim 1, wherein the emulsion in step (b) is made by emulsifying an alkenylsuccinic anhydride component, optionally containing a surfactant, with an aqueous polymer solution, and thereby forming an emulsion.
 24. A paper made by the process of claim
 1. 25. The paper of claim 24, wherein the paper is selected from the group consisting of paperboard papers, fine papers, newsprint papers, and combinations thereof.
 26. A method for sizing a paper product comprising: (a) providing a paper stock system; (b) forming, in the absence of high shearing forces, an aqueous sizing emulsion comprising an alkenylsuccinic anhydride component; wherein the emulsion is made in the presence of a cationic component under conditions, in the absence of high shearing forces, that produce an emulsion having improved sizing efficacy; (c) adding the emulsion to the paper stock; and (d) forming a paper web. 